Many websites serve users from around the world. There are different approaches to serving content appropriate to your users' language and/or region. Last year, we launched support for explicit annotations for web pages rendering the same content with different language templates.
Today we're going further with our support for multilingual content with improved handling for these two scenarios:

Multiregional websites using substantially the same content. Example: English webpages for Australia, Canada and USA, differing only in price

Multiregional websites using fully translated content, or substantially different monolingual content targeting different regions. Example: a product webpage in German, English and French

Specifying language and location

We've expanded our support of the rel="alternate" hreflang link element to handle content that is translated or provided for multiple geographic regions. The hreflang attribute can specify the language, optionally the country, and URLs of equivalent content. By specifying these alternate URLs, our goal is to be able to consolidate signals for these pages, and to serve the appropriate URL to users in search. Alternative URLs can be on the same site or on another domain.

Annotating pages as substantially similar content

Optionally, for pages that have substantially the same content in the same language and are targeted at multiple countries, you may use the rel="canonical" link element to specify your preferred version. We’ll use that signal to focus on that version in search, while showing the local URLs to users where appropriate. For example, you could use this if you have the same product page in German, but want to target it separately to users searching on the Google properties for Germany, Austria, and Switzerland. Update: to simplify implementation, we no longer recommend using rel=canonical.

Example usage

To explain how it works, let’s look at some example URLs:

http://www.example.com/ - contains the general homepage of a website, in Spanish

http://es-es.example.com/ - is the version for users in Spain, in Spanish

http://es-mx.example.com/ - is the version for users in Mexico, in Spanish

http://en.example.com/ - is the generic English language version

On all of these pages, we could use the following markup to specify language and optionally the region:

If you specify a regional subtag, we’ll assume that you want to target that region.
Keep in mind that all of these annotations are to be used on a per-URL basis. You should take care to use the specific URL, not the homepage, for both of these link elements.